Juumonji is the apparent leader of the "Ha-Ha Brothers." A few times, including the NASA Aliens game and the Death March, we see him as a leader who urges the other two to follow. He sports an X-shaped scar on his right cheek and is also the only one of the three to figure out that Sena was actually Eyeshield 21. He seems to be the most thoughtful (in a sort of positive way). He always seems to keep the three-some (includes him) together and is considered the "eldest brother" of the three. He gets fired up a lot. He is also the first of the three to score a touchdown. This in itself is a near-miracle, since his position almost NEVER handles the ball and he managed to get across the goal line. He is also the first to really become serious about football, occasionally sympathizing with Sena and vowing to become a better lineman in order to assist him. Juumonji also has an uneasy relationship with his father, since his father is always telling him not to associate himself with his friends, who he puts down as "trash" (like Agon does).

It is revealed that Juumonji is one of the smartest on the team- in an omake where the intelligences of the Devil Bats were compared, he ranked above everyone, but still below Hiruma, Mamori, and Yukimitsu. (Musashi was not included).

Musashi has commented that Juumonji is 'the same kind of guy as him', in terms of attitude (stoic and samurai-esque). Juumonji and Musashi tend to react the same way to outrageous incidents.

In the anime only, he suffers from acrophobia, a problem which Doburoku admits that not even finishing the Death March can fix.

His last name means "cross" most likely a reference to the scar on his cheek. It is possible the scar itself is hereditary as his father has the same scar on his forehead.